The present invention relates to a deceleration control device of a vehicle provided with a shift lever.
In a vehicle, shift down (i.e., move into low gear) is performed at a transmission to increase vehicle's deceleration in vehicle's traveling on a down slope or during rapid deceleration, for example. Japanese Patent Laid-Open Publication No. 9-317872 discloses a technology in which a shift map for engine brake is adjusted in accordance with the number of times of operation to a low speed stage (low-speed gear ratio). Japanese Patent Laid-Open Publication No. 2015-152053 discloses a technology in which an engine-brake force which is resistance of a power plant is changed in accordance with the number of times of operation of a shift lever from a D-range position to a B range which is provided beside the D-range position.
Further, there exists another technology which is practically applied to a vehicle provided with a multi-stage (multi-gear ratio) type of stepped automatic transmission, in which in a state where a shift lever is positioned at an M range provided beside a D range, a shift-down command for one-stage (one-gear ratio) shift down is outputted by operating the shift lever forward, and a shift-up command for one-stage (one-gear ratio) shift up is outputted by operating the shift lever rearward.
There exists further another practically-applied technology in which an S-range position and an L-range position are arranged in series relative to a D-range position. That is, in a case of a forward 5-stage (1st speed-5th speed of gear ratios) automatic transmission, for example, while an automatic gear change is performed among all shift stages of 1st speed-5th speed of gear ratios at the D-range position, the automatic gear change is performed among 1st speed-4th speed of gear ratios at the S-range position and the automatic gear change is performed among 1st speed-3rd speed of gear ratios at the L-range position so that the maximum shift stage to be obtained becomes a lower speed stage compared to a case of the D-range position.
Moreover, in a vehicle provided with an electric motor as the power plant in which a gear ratio (a speed ratio) of a transmission is fixed or there is no transmission, there exists a deceleration control device in which a shift lever is operable for selecting at least a D range, an R range, an N range (neutral range), a P range (parking range), and a B range and an M range which are selected for obtaining shift-down feeling of the automatic transmission which is expected when an accelerator is eased off.
The deceleration control using resistance which is caused by a loss or regeneration of the power plant in a driven state through above-described shift lever operation preferably reduces burden of a frictional type of brake device of a normal foot brake, suppresses wear of the brake device, or prevents vaper lock or fade phenomenon of the brake device in vehicle's traveling on a steep down slope.
A conventional device has a problem that the shift-lever operation for requesting the shift down needs plural times of operation when a driver conducts two or more stages of shift down for wanting large deceleration of the vehicle, so that the desired deceleration may not be obtained easily and promptly. That is, there is a concern that one-time operation of the shift lever for providing one-stage shift down may not achieve the desired deceleration. In this case, the shift down for the two-stage shift down may be finally required by operating the shift down twice, or the shift down for the three-stage shift down may be finally required by operating the shift down three times.
In particular, a recently-used multi-stage type of stepped automatic transmission adopts a forward many-stage type, such as a forward 8-stage, 9-stage, or 10-stage type, so that a change amount in the gear ratio between adjacent shift stages becomes so small that the one-stage shift down may not create sufficient deceleration any more.
Further, in the automatic transmission using the S range or the L range, since the maximum shift stage to be obtained is merely restricted, there may exist a case where the shift down is not performed when the shift lever is operated from the D range to the S range or the L range. That is, when the current shift stage in the D range corresponds to the shift stage which is lower than the maximum shift stage to be obtained in the S range or the L range, no shift down may be performed even if the shift lever is operated to the S range or the L range.